Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$227.47	6.209%	$241.5936	$241.59	$241.60	$241.60
Purchase #2	$37.75	10.673%	$41.7791	$41.78	$41.80	$41.80
Purchase #3	$32.86	12.545%	$36.9823	$36.98	$37.00	$37.00
Purchase #4	$146.42	8.277%	$158.5392	$158.54	$158.55	$158.50
Purchase #5	$216.60	11.480%	$241.4657	$241.47	$241.45	$241.50
Purchase #6	$189.83	11.670%	$211.9832	$211.98	$212.00	$212.00
Purchase #7	$222.38	7.447%	$238.9406	$238.94	$238.95	$238.90
7 purchase totals =	$1,073.31		$1,171.2837	$1,171.28	$1,171.35	$1,171.30